It has been a long recognized problem that during production of hydrocarbons, particularly from gas wells, liquids, primarily water, accumulate in the wellbore. As the liquid builds at the bottom of the well, a hydrostatic pressure head is built which can become so great as to overcome the natural pressure of the formation or reservoir below, eventually “killing” the well.
A fluid effluent, including liquid and gas, flows from the formation and through perforations in the casing. Liquid accumulates as a result of condensation falling out of the upwardly flowing stream of gas or from seepage of liquids from the formation itself. To further complicate the process, the formation pressure typically declines over time. Once the pressure has declined sufficiently so that production has been adversely affected, or stopped entirely, the well must either be abandoned or rehabilitated. Most often the choice becomes one of economics, wherein the well is only rehabilitated if the value of the unrecovered resource is greater than the costs to recover it.
Many techniques have been utilized to attempt to remove liquids which have accumulated in the wellbore. Of these many techniques some are focused on lifting liquids uphole to the surface, such as in gas or plunger lift systems. Other techniques have been focused on pumping water below the producing zone and into a lower portion of the formation that can act as a reservoir to accommodate the pumped water. These techniques are typified by arrangements that collect liquids below a conventional uphole-pumping pump, pump them slightly uphole and then route them back downhole through bypass tubing. These arrangements are subject to loss of head pumping failures in attempting to establish suction under low head conditions to pump uphole.